This invention relates to energy storage systems. More particularly it relates to systems for utilizing stored energy during peak demand periods.
This invention is an improvement over U.S. Pat. No. 4,735,064 issued Apr. 5, 1988 and invented by Harry Fischer and is hereby incorporated herein by reference.
The tank or container which is shown in the Fischer Patent to store energy during one time period, generally at night, and to supply energy during peak periods of energy use, generally in late afternoon, may also be used herein. Preferably the stored energy is used for cooling buildings during summer months.
There are primarily two practices commonly followed to avoid high utility demand charges during peak summer hours. One is called load shedding in which compressors are shut down during the peak periods and cooling is provided by stored energy, such as by using large tanks of chilled water or by melting large quantities of ice to provide cooling. The size of such systems is large because all of the cooling must be provided from storage. During charging periods, a large mechanical system must be used to recharge the system in the allotted off-peak charging period.
Another system used to reduce peak demand is called load leveling. In that case, a smaller mechanical package is required and a smaller energy storage tank is required. In the case of load leveling, the small mechanical package is designed to meet the peak day requirement by operating 24 hour per day. During night-time periods of low air conditioning loads, the excess capacity is used to build ice in an energy storage container. During daytime operation, the mechanical package or condensing unit operates to meet the cooling requirements of the building. When the cooling requirements are satisfied, the condensing unit continues to store more cooling. When the cooling load exceeds the capacity of the condensing unit, some of the stored energy in the form of ice is melted to condense some of the refrigerant to supplement the condensing unit capacity to meet the peak loads.
Ice freezing time of low air conditioning demand may be as long as 12-14 hours, contrasting to the peak demand hours, which may be as short as 3 hours or as long as 10 hours. This invention covers a novel load leveling system which, in conjunction with the Energy Storage Container described in the Fischer Patent, provides a simple, energy efficient, and low cost means of meeting the varying cooling loads required to satisfy the need of both residential and commercial buildings that are cooled by "direct expansion" cooling systems. While the system described in the Fischer patent also provides these results, it uses an electrical pump to move refrigerant during the peak demand and thus requires the use of electrical energy during that time.